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Steady rotation of the Cascade arc

Geology

By:
,
DOI: 10.1130/G34514.1

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Abstract

Displacement of the Miocene Cascade volcanic arc (northwestern North America) from the active arc is in the same sense and at nearly the same rate as the present clockwise block motions calculated from GPS velocities in a North American reference frame. Migration of the ancestral arc over the past 16 m.y. can be explained by clockwise rotation of upper-plate blocks at 1.0°/m.y. over a linear melting source moving westward 1–4.5 km/m.y. due to slab rollback. Block motion and slab rollback are in opposite directions in the northern arc, but both are westerly in the southern extensional arc, where rollback may be enhanced by proximity to the edge of the Juan de Fuca slab. Similarities between post–16 Ma arc migration, paleomagnetic rotation, and modern GPS block motions indicate that the secular block motions from decadal GPS can be used to calculate long-term strain rates and earthquake hazards. Northwest-directed Basin and Range extension of 140 km is predicted behind the southern arc since 16 Ma, and 70 km of shortening is predicted in the northern arc. The GPS rotation poles overlie a high-velocity slab of the Siletzia terrane dangling into the mantle beneath Idaho (United States), which may provide an anchor for the rotations.

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Additional Publication Details

Publication type:
Article
Publication Subtype:
Journal Article
Title:
Steady rotation of the Cascade arc
Series title:
Geology
DOI:
10.1130/G34514.1
Volume
41
Issue:
9
Year Published:
2013
Language:
English
Publisher:
Geological Society of America
Contributing office(s):
Geology, Minerals, Energy and Geophysics Science Center
Description:
4 p.
Larger Work Type:
Article
Larger Work Subtype:
Journal Article
Larger Work Title:
Geology
First page:
1027
Last page:
1030
Number of Pages:
4
Country:
Canada;United States